Duplex telegraphy



(No Model.) G. W. GARDANIER. DUPLEX TELEGRAPHY.

Patented Apr. 19, 1887.

I k a v l 1 Z A RS. Phutn-Lkhographer. Walhjnglnn.

I rTED STATES PATENT OFFICE,

GEORGE W. GARDANIER, OF NEWV YORK, N. Y., ASSIGNOR TO THE BALTI- MOREAND OHIO TELEGRAPH COMPANY, OF BALTIMORE, MARYLAND.-

DUPLEX TELEGRAPHY.

SPECIFICATION forming part of Letters Patent No. 361,356, dated April19, 1887.

Application filed September 23, 1885. Serial No. 177.888. (No model.)

To all whom it may concern.-

Beit knownthat I, GEORGE W. GARDANIER, a citizen of the United States,residing in the city of New York, in the county and State of New York,have invented certain new and useful Improvements in Duplex Telegrapny,of which the following is a specification.

The invention relates to the organization of circuits and apparatus forpreventing the false signals which are liable to be produced upon thereceiving-i nstruments at the home stations of duplex and quadruplextelegraphs by reason of the momentary currents due to the staticinduction of the main line.

The invention consists in combining, with a transmitting apparatusadapted to send currents from a suitable source to the main line and areceiving instrument included in a Wheatstone bridge, a condenserinterposed in a conductor leading from the main-line circuit to theearth at the home station through a second set of coils wound upon thecores of the receiving-instrument. The discharge of the condenser, uponthe interruptionof the bat 'tery-circuit, causes an impulse to traversethe second or supplemental set of coils upon the receiving-instrument.This impulse tends to neutralize the effect of the discharge of the mainline which takes place across the bridge. conductor of the YVheatstonebridge. The discharge from the condenser to the main line also tends toneutralize the line-discharge by passing from the plate to the line andthere meeting and opposing it. 4

The accompanying drawing is a diagram showing an organization of thecircuits and apparatus at one station.

Referring to the drawing, L represents the main line over which it isdesigned to transmit currents from the battery 0 by means of a key, K.The battery has'one pole connected with the earth at E by a conductor,1, and its other pole is connected by conductor 2 with the front stop,k, of the key K. The backstopk of this key is connected with the earthat e by a conductor, 3. The lever 7c of the key is connected by aportion, Z, of the main line with the meeting-point a of the two arms tow of a Wheatstone bridge. The arm to is connected at a point, a, with anartificial line, Z, which leads through an artificial reto line.

sistance, T, to the earth ate. The bridgeconductor 10" leads from thepoint a to the point a through the coils r and r of areceiving-instrument, R. It is evident that the outgoing currents willdivide at the point a, a portion going over the main line and a portionto the earth at e by way of the bridge 10 and the artificial line Z. Noeffect, therefore, will be produced upon the receiving-instru' mcnt R.The incoming currents, however, arriving at the point 11 may find theirway to the earth either through the bridge-wire 10 and the artificialline Z or by way of thearm 10, line Z, and key K. It the latter is atrest against its back-stop k then the circuit will be completed from theline Z,- by the conductor 3, to the earth at 0 otherwise through theconductor 2 and battery 0 and conductor 1 to the earth at E.

Leading from a point, 4, in the line L is a conductor, 5, connected withone side, 0, of a condenser, O. The other side, a, of the condenser isconnected by a conductor, 6, through a the supplemental coils r and 7*,upon the cores of the receiving-instrument R, and from these coils theconnections are completed, by the conductor 7, with the earth at c".

When the circuit of the battery 0 is completed with the main line by thekey K, the condenser 0 receives upon its plate 0 a positivecharge andupon the plate 0 a negative charge, considering that ,the positive poleis Upon the interruption of the circuit there is a tendency for the lineL to discharge through the coils 1 and 1' sending a positive impulsefrom the point a" to the point ed. The effect produced by the dischargeof the condenser O is to neutralize the effect of the discharge of theline. The charge taken by the plate 0 will be negative, or the oppositeof that received by the line, and therefore the coils r and 0" must beso wound that the impulse from the condenser-plate 0 will circulate inthe opposite direction from the current from the line. In this mannerthe effect of the discharge of the condenser will be to neutralize themagnetism which would otherwise be produced in the cores of theinstrument It by the discharge-current traversing the coils r and 1- Iclaim as my invention- 1. The combination, substantially as hereinbeforeset forth, of a main line, a Wheatstone bridge, a receiving-instrumentin the bridge, supplemental coils upon the receiving-instrubridge-wirewith the earth, a condenser, eonductors connecting the respective platesof the same with the battery and the earth, and com- 15 ment, and acondenser having one plate eonpensating coils applied to thereceiving-instru- 5 nected with the main line and the other plate mentincluded in said conductors.

connected, through said supplemental coils, In testimony whereof I havehereunto subwith the earth. scribed my name this 8th day of September,

2. The combination of a' main line, a but A. D. 1885. tery, aXVheatstone bridge, means for connect- IO ing said battery with the armsof said bridge,

a receiving-instrument included in the bridge- GEORGE W. GARDANIER.\Vitnesses:

J AMES II. ELLIS,

conductor, an artificial line connecting the FRANK A. lnmsox.

